Web page content is commonly personalized for particular users based on one or more demographic, usage, or other characteristics of the particular users. For example, if a young male consumer requests a web page associated with an Internet website, and a determination of these characteristics (young and male) can be made at the website, the requested page might be rendered at the website to include an advertisement for a red sportscar based on these characteristics. Such personalization allows advertisements to be presented to their target audiences—those most likely to purchase products, services, or other items in response to the advertisements—to increase sales of these items. When a consumer responds favorably to such a personalized advertisement, attempting to buy the item to which the advertisement is directed, but the item is not in stock, cannot be delivered within an acceptable time, or is otherwise unavailable, the consumer may often become disappointed, frustrated, or even angry with the seller. This may actually result in lower sales for the seller, as such consumers attempt to purchase the requested item, and perhaps future items, from other on-line sellers or decrease their on-line shopping in general. As a result of these or other disadvantages, previous techniques for rendering content have been inadequate for the needs of many sellers.